SPERMATOPHYTES 



207 



(5) GlNKGOALES 



General character. Ginkgo biloba, the maidenhair tree, is the only 

 living representative of a gymnosperm line that reaches back to the 

 paleozoic Cordaitales, and was most extensively displayed during the 

 Mesozoic. Its extensive cultivation by the Chinese and the Japanese, 

 especially in temple grounds, first brought it into notice, and for a long 

 time it was supposed that it did not exist in the wild state. In recent 

 years, however, it has been found growing wild in the mountains of 

 western China. 



FIG. 465. The leaf of Ginkgo. 



Sporophyte. Ginkgo is a tree with the general habit of a conifer, 

 and therefore very unlike a cycad. As in both Cordaitales and Conif- 

 erales, it develops two kinds of branches : long shoots bearing scattered 

 foliage leaves, and dwarf shoots bearing a few crowded leaves. 



Vascular anatomy. The anatomy of the stem closely resembles 

 that of the Coniferales, with its thick cylinder of secondary wood and 

 its relatively small pith, the latter character contrasting with the large 

 pith of Cordaitales. All traces of mesarch bundles have disappeared 

 from the stem, and also from the leaves, but they occur in the cotyle- 

 dons. It is evident that in vascular anatomy Ginkgo has departed 

 farther from the ferns than have the Cordaitales or the cycad line. 



